An organic silicon resin is a three-dimensional structural body having silicon of a Q-unit (SiO4/2) and a T-unit (RSiO3/2) (R represents, for example, a monovalent organic group) as essential components. An organic silicon resin having a strong skeleton shows characteristics such as weather resistance, heat resistance, water repellency, and electric insulation, so that it is used in a pressure-sensitive adhesive, a rubber compound, a releasing agent, a coating material, etc. In recent years, demands as raw materials of cosmetics such as foundation, eye-shadow, cream, milky lotion, and hair cosmetic are also increasing because part of the organic silicon resins has a film forming property.
Further, when the organic silicon resin is modified with an organic functional group, new characteristics other than the characteristics can be added. For example, when the resin is modified by a hydrophilic group such as polyether, it can be provided with hydrophilicity. Because general organic silicon resins use organosilanes and disiloxanes such as (CH3)3SiCl, (CH3)3SiOSi(CH3)3, and (CH3)3SiOH as the source of an M-unit (R3SiO1/2), the surface thereof is covered with a trimethylsilyl group, so that they are very hydrophobic. Therefore, when it is provided with a hydrophilic group, a resin having a water retaining property can be synthesized (Patent Document 1). Also, when it is modified with a reactive functional group such as an epoxy group, the resin can be used as a thermosetting resin for an optical semiconductor such as LED (Patent Document 2 and Patent Document 3). Further, when it is modified with a short chain alkyl group, the resin can be applied as a resin additive in a pigment-containing cosmetic blend (Patent Document 4).
As the method for introducing an organic functional group to the organic silicon resin, (1) a post-grafting method (grafting method) and (2) a co-condensation method may be mentioned. In the method (1), for example, by silylating a surface silanol group of an organic silicon resin with a chlorosilane such as R3SiCl, an organic group can be introduced into it. However, because complete control of amount of the silanol group on the organic silicon resin surface is difficult, there is a problem that accurate control of the amount of the modifying organic group is difficult. Besides, because a strong acid is generated at the time of silylation reaction, there is a possibility that bonds of the organic silicon resin are broken. In the method (2), for example, by co-condensation of two alkoxysilanes with the Q-unit (SiO4/2) and with the T-unit (RSiO3/2) (part of R is an organic functional group), an organic functional group can be introduced by one-pot. However, because hydrolysis properties of these two alkoxysilanes are different, it has been difficult to obtain the organic silicon resin having the Q-unit and T-unit uniformly dispersed.
On the other hand, as to the active point of the organic silicon resin having a reaction active point usable in the grafting method (1), besides the silanol group, a vinyl group may be mentioned. To the organic silicon resin having a vinyl group, an organic group can be introduced by a hydrosilylation reaction with a hydrosilyl group-containing organic compound or a thiolene reaction with an organic group having a thiol group. However, organic compounds having a hydrosilyl group or a thiol group are not so many that the introducible organic groups are limited. Alternatively, a hydrosilyl group may also be considered as the reaction active point. To the hydrosilyl group-containing organic silicon resin, an organic group can be introduced by a hydrosilylation reaction with an organic compound having a vinyl group or an allyl group. Because there are many organic compounds having a vinyl group or an allyl group, by using this method, organic silicon resins having various organic groups can be obtained.
As to the method for producing the hydrosilyl group-containing organic silicon resin, there is a method in which a chlorosilanes such as dimethyl chlorosilane or methyl dichlorosilane is caused to react with the silanol group on surface of the organic silicon resin. However, chlorosilanes have so high reactivity that they are prone to undergo hydrolysis condensation by themselves; and thus, there is a problem that the hydrosilyl group cannot be quantitatively introduced to the resin. Alternatively, a method is proposed that diorganopolysiloxane or tetraorganodisiloxane, both having the hydrosilyl group, is added to the synthesized organic silicon resin followed by a re-equilibration reaction so as to introduce the hydrosilyl group (Patent Document 5). However, with this method, the introducible amount of the hydrosilyl group is so small; and thus, it is considered that introduction of a large amount thereof is difficult.
Further, by co-hydrolysis condensation reaction of a chlorosilane having the hydrosilyl group (Patent Document 6 and Patent Document 7), or of a hydrogenated halosilane (Patent Document 8), the hydrosilyl group-containing organic silicon resin can also be produced; in these methods, however, there are problems such as lowering of the molecular weight and a low hydrogen content. Alternatively, a method in which a hydrosilicone oil is added to the hydroxyl group-containing organic silicon resin by way of a dehydrogenation reaction is proposed; however, the form of the organic silicon resin obtained by modification with a flexible silicone is limited to a liquid (Patent Document 9).